Plate 28. 

 1, 2. Dermatodiadema horridum A. Ag. 



1. Abactinal system of a specimen measuring 20 mm. in diameter with 7-8 



tubercles ; Station 3413. 



2. Abactinal system of another specimen of the same size as fig. 1, with smaller a; 



crowded anal plates ; Station 3413. 



3, 4. Dermatodiadema globulosum A. Ag. 



3. Abactinal system of a specimen measuring 25 mm. in diameter; Station 3398. 



4. Abactinal system of a specimen measuring 30 ram. in diameter; Station 3381. 



